A functionalized TiO2/Mg2TiO4 nano-layer on biodegradable magnesium implant enables superior bone-implant integration and bacterial disinfection

Rapid corrosion of biodegradable magnesium alloys under in vivo condition is a major concern for clinical applications. Inspired by the stability and biocompatibility of titanium oxide (TiO2) passive layer, a functionalized TiO2/Mg2TiO4 nano-layer has been constructed on the surface of WE43 magnesium implant by using plasma ion immersion implantation (PIII) technique. The customized nano-layer not only enhances corrosion resistance of Mg substrates significantly, but also elevates the osteoblastic differentiation capability in vitro due to the controlled release of magnesium ions. In the animal study, the increase of new bone formation adjacent to the PIII-treated magnesium substrate is 175% higher at post-operation 12 weeks, whereas the growth of new bone on titanium control and untreated magnesium substrate are only 97% and 29%, respectively. In addition, its Young's modulus can be restored to about 82% as compared with the surrounding matured bone. Furthermore, this specific TiO2/Mg2TiO4 layer even exhibits photoactive bacteria disinfection capability when irradiated by ultraviolet light which is attributed to the intracellular reactive oxygen species (ROS) production. With all these constructive observations, it is believed that the TiO2/Mg2TiO4 nano-layer on magnesium implants can significantly promote new bone formation and suppress bacterial infection, while the degradation behavior can be controlled simultaneously.